Alcohol is classified pharmacologically as a central nervous system depressant. The mechanisms that underlie this alcohol-induced depression of nervous system excitability, however, are poorly understood. This project investigated the intrinsic mechanisms involved in the regulation of nerve cell excitability and the effects of ethanol on those mechanisms. Experiments were conducted to determine whether axonal tracing methods for identifying neurons can be used in conjunction with the whole-cell patch-clamp technique for studying neuronal excitability mechanisms. The fluorescent dyes Fast Blue and Fluoro-Gold were injected into the wall of the urinary bladder, colon or various somatic structures, in an attempt to label postganglionic neurons in the major pelvic ganglion, as well as visceral and somatic neurons in the lumbosacral dorsal root ganglia and trigeminal ganglion. One to three weeks after dye injection, neurons were isolated from ganglia by enzymatic dissociation. After isolation, single neurons labeled with Fast Blue were identified in the three types of ganglia studied. Fluoro- Gold, however, was identified consistently only in trigeminal neurons. After exposing the isolated neurons to UV light for 10-20 seconds, which was necessary for identification of the neurons, the electrophysiological properties of the Fast Blue-labeled cells did not differ from those of unlabeled cells. However, a more prolonged exposure of the neurons to UV light for 1-5 minutes produced deterioration of the action potential, sodium current and resting membrane potential; these changes did not reverse during the course of the experiment, suggesting that they reflect irreversible damage to the cells. The results indicate that the whole- cell patch-clamp technique can be used in combination with axonal tracing methods for studying the excitability mechanisms of identified populations of neurons. In addition, the effect of ethanol was tested on the intrinsic excitability mechanisms in several different types of neurons and it was found to have little or no effect on several types of voltage-gated ion channels in a pharmacologic concentration range (5- 100mM).